Process of treating iron ores with tar



United States Patent p 2,812,248 rnocnss F TREATING IRON' onus WITH'TAR Joseph Becker, Pittsburgh, Pa, a'ssignor'i to Koppers Company, Inc., a corporation of- Delaware No Drawing. Application Novemher 6, 1953, Serial No. 390,757

6 Claims. (Cl. 75[' The present invention relates toan improvement in the process of treating iron oxide-bearing materials according to my copending applications Serial No. 359,655, filed June 4, 1953, and Serial No. 383,907, filed October 2, 1953, of which this application is a continuation-in-part wherein such materials are mixed with a small part of a total charge of coals destined for high temperature coking for use conjo'intly as the coke for metallurgical purposes with such iron oxide materials, the mixture coked in slot ovens and the final product of coking ultimately treated by use for metallurgical purposes with the remainder of the total coke charge. 7 More particularly, the present invention relates to an improvement in this process whereby tar containing iron-bearing dust, produced by the coking step for coking a small part of the total charge, is collected separately from the collection of tar produced by the coking of the remainder of the total coke charge and is utilized by recycling to other charges destined for coking.

The tar as ordinarily produ'ced heretofore from the coking of mixtures of iron oxide-bearing materials and coal contains iron-bearing dust has been carried over into the collecting main, common to all of the ovens for the total coke charge with the raw gas from all of the ovens of the slot type. The presence of the iron-bearing dust in the tar makes all the tar or the pitch produced therefrom in the ovens for the total charge unsuitable for many normal usages. 7

One of the features of the present invention is to provide a process wherein tar contaminated with iron-bearing dust is separately collected from the collection of tar from the remaining ovens and converted into a useful material in combination with my aforesaid coking process whereby an increase of gas, light oil and coke is obtained from the unsuitable tar in said coking process, leaving the tar collected from the remaining ovens suitable for the many normal usages.

It will be obvious to one skilled in the art that various changes can be made in the several steps of the process disclosed hereinafterwithout departing from the scope of spirit of this invention.

In carrying out the present invention, a part of the total coal charge is mixed with iron oxide-bearing materials in regulated proportions, such as disclosed in my aforesaid copending applications and coked, as disclosed therein in part of the 'ove'ns, the remaining ovens taking care of the coking of the remainder of the total coal charge destined for coking to produce the total coke for metallurgical purposes with said iron oxide material and the resulting iron-coke product used for metallurgical purposes. The tar condensed in the collecting mains from the raw gas produced from the coking of such mixtures in the coke ovens there referred to contains the ironbearing dust which is carried over into the collecting main with the raw gas and whose presence makes the tar or the pitch produced from this tar unsuitable for many normal uses of such material.

In one advantageous embodiment of the present invention, this tar is collected separately from the collection 2,812,248 Patented Nov. 5, 19 57 of tar from the remainder of the ovens and recycled to bemix'ed with another charge to the ovens. The t-ar'with the iron bearing dust returned to another oven charge from the ovens charged with the iron-coke mixture can consist of all of the tar from said ovens or can consist of only the collecting main tar from said slot ovens. In the latter event, the tar condensed in the primary coolers and in subsequent by-product equipment following the collecting main for such ovens, which will be substantially free of iron-bearing dust, can be mixed therein with normal tar produced from ovens charged with straight coal.

The principle of separately collecting and recirculating the tars to another oven charge is elfectively employed as follows in combination with the processes that have beenset forth in my copending applications, Serial No. 359,655 and Serial No. 383,907. For example, in carrying out the process disclosed in my application Serial No. 359,655 wherein iron oxide-bearing materials are mixed with asmall portion of a total coal charge destined for coking chambers of the slot type with high temperature" coking at a rate of one inch per hour by heat applied indirectly laterally inwardly of. the masses in" the chambers, coked thereby in chambers separately from the coking in other chambers of the larger portionv of straight coal, in order that the small portion of the coal and coke therefrom; will contain alarge percentage of iron oxide-bearing materials, and. the separately coked portions are thereafter" used conjointly for metallurgical purposes, the tar is collected from. the gas issuing from the step of coking the small portion of the total coke charge and containing ironbearing dust separately from the collection of tar from the gas from the coking of the larger portion of straight coal, and. is recirculated and mixed with another small portion of atotal coal charge destined for such coking as the small portion containing iron oxide-bearing mate'- rials. Or, if so desired, the tar containing iron-bearing" dust can be mixed with the charge to all the ovens including the ovens charged with straight coal. I

As set forth in the cop'ending application Serial No. 359,655, the percentage of the small portion of coal that is mixed with iron oxide-bearing materials to the total charge for all said coking chambers can range from about 5% to about 45% and in a preferred embodiment of the invention ranges from about 8% to about 25%. The quantity of iron oxide-bearing materials, which can be taconite, magnetite or hematite ores or blast furnace fine, dust, mixed with a small portion of the total coal charge destined for coking chambers can vary from approxi{ mately 20% to approximately 65% by weight of the small portion.

The quantity of iron-bearing material in the tar that is I recycled is so small as to have little, if any, deleterious effect on the by-product yield of these ovens. For ex ample, if 20% of the ovens in a particular plant are utilized to produce iron-coke and of theovens are; charged with straight coal, the tar yield from the 20% of the ovens which produce iron-coke is approximately eight (8) gallons of tar per ton of coal present in the iron and coal charged mixture or five (5) gallons er ton of total iron and coal mixture charged to said 20% of the ovens, the mixture comprising 62.5% coal and 37.5% iron oxide-bearing materials. Further, if all the tar produced in said 20% of the ovens is recycled and admixed with another like charge destined to be coked in20% of the ovens producing iron-coke, it would be such a quantity as to make up 2.5% by weight of such a mixture. If only the collecting main tar from the iron-coke ovens is recycled and admixed with another like charge destined to be coked in ovens producing iron-coke, it would be such a quantityas to make up 1.7% by weight of such a mixture. If all the tar collected from the 20% of the ovens operated asiron-coke ovens is mixed uniformly with the charge to all the ovens in the plant, that is, those that are operated for coking straight coal as well as those that are operated as iron coke ovens, the tar from the iron coke ovens in the mixture would be about 0.5% by Weight of the total oven charge for both kinds of coke, and if only the collecting main tar from the iron-coke ovens is mixed uniformly with the charge to all the ovens for both kinds of coke in the plant, the tar in the oven charge for each oven would be about 0.35% by weight. Since the percentage of iron-bearing material in the collecting main tar from such 20% 'of the ovens operated for iron coke is small, ordinarily being substantially less than 10% of the tar, it is obvious that the addition of such material to the charge to all ovens in the plant will result in the addition of less than 0.05% iron-bearing material to the mixture charged to the ovens which are not producingiron-coke.

In carrying out the process disclosed in my copending application Serial No. 383,907, wherein iron oxide-bearing materials are mixed with the small portion of coal, the mixture coked for a period of two to six hours longer than that normally required for the satisfactory coking of the straight coal alone at a rate of one inch per hour, and the resulting iron-coke product is used for metallurgical purposes, the tar containing iron-bearing dust produced by said separate collection from this coking step can be recycled and mixed with another charge to be coked in similar fashion. The resulting iron-coke produced will have a maximum metallic iron content, in-' creased size and strength, the recycled tar permitting a closer contact between the coal and the iron oxide-bearing materials already present in the mixture and the iron dust present in the recycled tar adding to the iron content of the coked product.

It is to be understood that the smallest quantities of tar can be recycled and, in those instances where the mix is such that it is desirable to obtain closer bonding be tween the coal and the iron-oxide material, the amount of tar recycled should constitute at least about 1% and preferably about 2% by weight of the charge to which it is added.

The relative percentages and types of the iron oxidecoal mixture can vary in accordance with the percentages set forth in the aforementioned copending application Serial No. 383,907, as can the periods of coking time as set forth in that application.

In still another advantageous embodiment of the present invention, tar is collected separately from iron-coke ovens, distilled in separate distillation equipment, and the lighter fractions of the tar collected as distillate, producing thereby a still residue or pitch containing essentially all the iron-bearing dust that was present in the original tar from the iron-coke ovens. This, then is recirculated and mixed with a charge containing iron oxide-bearing materials or mixed to a total charge, a portion of which is straight coal and a portion of which is a mixture of coal and iron oxide-bearing materials. It is to be understood that the tar collected and distilled separately by this method can be either the total tar produced from the iron-coke ovens or can be only the collecting main tar from the iron-coke ovens.

The aforedescribed methods provide means for converting contaminated tar produced by ovens which produce iron-coke to useful material. Depending upon the way this tar is collected and handled, the tar from the ironcoke ovens can be converted to a slightly lower yield of iron free tar, together with a slightly increased yield of gas, light oil, and coke; or, if the total tar from the ironcoke ovens is recycled only to the iron-coke ovens, the tar will be ultimately converted to gas, light oil, and coke.

The invention claimed is:

1. A process of treating iron oxide-bearing materials comprising the steps of mixing iron oxide-bearing materials with a small portion within the range of 5% to 45% of a total coal charge destined for high temperature coking, for use conjointly as the total coke for metallurgical purposes with said iron oxide material, in coking chambers of the slot type with high temperature coking at a rate of one inch per hour by heat applied indirectly laterally inwardly of the masses in the chambers so that said small portion of said total coal charge will contain 20 to 65% by weight of iron oxide-bearing materials and the remaining larger portion of said total coal charge will be straight coal; separately coking said portions of said total charge in said coking chambers as aforesaid; processing said separately coked portions conjointly for metallurgical purposes; collecting the tar from the gas issuing from the coking of the small portion separately from the collection of tar from the gas issuing from the coking of the larger portion; and recycling at least a portion of the separately collected tar containing iron-bearing dust produced by the separate coking of said small portion to another portion of a coal charge which is, destined to be coked in the aforesaid process.

2. The process of claim 1 wherein said small portion of iron oxide-bearing coal mixture comprises coal within the range of 8 to 25 percent of said total coal charge, and wherein said small portion of iron oxide bearing coal mixture is coked for a period of two to six hours longer than that normally required for the satisfactory coking of the straight coal.

3. A process as claimed in claim 1, wherein at least a portion of the recycled tar containing iron-bearing dust, which has been separately collected from said small portion coking step which contains iron oxide-bearing materials, is recycled to another total charge, including the larger portion of such total charge comprising straight coal.

4. A process as claimed in claim 1, wherein at least a portion of the recycled separately collected tar containing iron-bearing dust produced by said small portion coking step is recycled to the small portion of the total charge of another charge to be coked.

5. The process of claim 1, wherein at least a portion of said recycled separately collected tar containing iron oxidebearing materials produced by said small portion coking step is distilled and only the heavier fractions of said tar containing iron oxide-bearing materials are recycled to the coal for a next coking charge.

6. The process of claim 1 wherein the recycled tar consists of tar from the collecting main for gas issuing from said small portion coking step and the residual uncondensed tar in the gas from the main for said small portion coking step is mixed and condensed in primary coolers and subsequent by-product equipment with normal tar produced from ovens charged with straight coal.

References Cited in the file of this patent UNITED STATES PATENTS 52,554 Fleury Feb. 13, 1866 803,792 Sheldon 1. Nov. 7, 1905 1,467,797 Klugh Sept. 11, 1923 1,665,665 Jahnke Apr. 10, 1928 1,711,153 Mclntire Apr. 20, 1929 1,858,274 Kern et a1 May 17, 1932 1,896,088 Kern Feb. 7, 1933 1,941,983 Gudmundsen Jan. 2, 1934 2,077,651 Weaton Apr. 20, 1937 2,397,993 Urquhart Apr. 9, 1946 2,473,987 Brandon June 21, 1949 2,512,076 Singh June 20, 1950 2,536,365 I-Iandwerk et a1. Jan. 2, 1951 FOREIGN PATENTS 367 Great Britain of 1874 501 Great Britain of 1903 1,519 Great Britain of 1903 2,607 Great Britain of 1866 265,228 Great Britain Oct. 6, 1927 373,166 Great Britain -1 May 13, I932 400,933 Great Britain Oct. 30, 1933 

1. A PROCESS OF TREATING IRON OXIDE-BEARING MATERIALS COMPRISING THE STEPS OF MIXING IRON OXIDE-BEARING MATERIALS WITH A SMALL PORTION WITHIN THE RANGE OF 5% TO 45% OF A TOTAL COAL CHARGE DESTINED FOR HIGH TEMPERATURE COKING, FOR USE CONJOINTLY AS THE TOTAL COKE FOR METALLURGICAL PURPOSES WITH SAID IRON OXIDE MATERIAL, IN COKING CHAMBERS OF THE SLOT TYPE WITH HIGH TEMPERATURE COKING AT A RATE OF ONE INCH PER HOUR BY HEAT APPLIED INDIRECTLY LATERALLY INWARDLY OF THE MASSES IN THE CHAMBERS SO THAT SAID SMALL PORTION OF SAID TOTAL COAL CHARGE WILL CONTAIN 20 TO 65% BY WEIGHT OF IRON OXIDE-BEARING MATERIALS AND THE REMAINING LARGER PORTION OF SAID TOTAL COAL CHARGE WILL BE STRAIGHT COAL; SEPARATELY COKING SAID PORTIONS OF SAID TOTAL CHARGE IN SAID COKING CHAMBERS AS AFORESAID; PROCESSING SAID SEPARATELY COKED PORTIONS CONJOINTLY FOR METALLURGICAL PURPOSES; COLLECTING THE TAR FROM THE GAS ISSUING FROM THE COOKING OF THE SMALL PORTION SEPARATELY FROM THE COLLECTION OF TAR FROM THE GAS ISSUING FROM THE COKING OF THE LARGER PORTION; AND RECRYLING AT LEAST A PORTION OF THE SEPARATELY COLLECTED TAR CONTAINING IRON-BEARING DUST PRODUCED BY THE SEPARATE COKING OF SAID SMALL PORTION TO ANOTHER PORTION OF A COAL CHARGE WHICH IS DESTINED TO BE COKED IN THE AFORESAID PROCESS. 